This application claims the priority of International Application No. PCT/DE05/000471 filed Mar. 16, 2005, and German Patent Document No. 10 2004 015 301.9, filed Mar. 29, 2004, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a rotor blade, particularly for a gas turbine.
Rotor blades of gas turbines are attached to a rotor of the gas turbine, particularly to rotor disks of the rotor, usually by blade roots, such that the blade roots engage in openings formed within the rotor or the rotor disk. The inner contour of the openings corresponds to the outer contour of the blade roots. The prior art essentially distinguishes two blade root configurations, i.e., the fir tree configuration and the dovetail configuration.
In the fir tree configuration, the cross-sectional contour of the blade root is characterized by a wave-shaped contour in both a front region of the rotor blade as seen in the direction of rotation and a rear region as seen in the direction of rotation, such that projections of this wave-shaped contour form a plurality of anchoring teeth in both of these regions. A corresponding opening within the rotor or the rotor disk into which the rotor blade may be inserted with the blade root has a complementary wave-shaped contour. A rotor blade with a fir tree configuration of this type is disclosed, for example, in the German publication DE 196 03 388 C1.
By contrast, in the dovetail configuration of the blade root, the cross-sectional contour is characterized by a continuous widening of the blade root from the radial outside to the radial inside, so that one anchoring tooth each is formed in both the front region and the rear region of the blade root as seen in the direction of rotation.
According to the prior art, both the fir tree configuration and the dovetail configuration for a blade root of a rotor blade are characterized by a symmetrical design of the blade root, i.e., by an equal number of anchoring teeth in both the front region and the rear region of the blade root as seen in the direction of rotation.
Based thereon, the object of the invention is to provide a novel rotor blade for a gas turbine and a corresponding gas turbine.
According to the invention, the blade root is designed asymmetrically, such that more anchoring teeth are associated with a front region of the blade root as seen in the direction of rotation than a rear region of the blade root as seen in the direction of rotation.
According to the present invention, an asymmetrical or non-symmetrical blade root design is proposed. It is distinguished in that the number of anchoring teeth provided in the front region of the blade root as seen in the direction of rotation differs from that in its rear region as seen in the direction of rotation. The axial length of the rotor and therefore also the weight of the rotor remains unchanged. The front region of the blade root as seen in the direction of rotation has a larger number of anchoring teeth than its rear region as seen in the direction of rotation. An asymmetrical blade root design of this type significantly reduces the tensile stresses that occur when the gas turbine is in operation and thus when the rotor and the rotor blade are rotating. This reduces the stresses acting on the blade root and increases the service life thereof.
According to a first advantageous embodiment of the invention, the front region of the blade root as seen in the direction of rotation has a fir tree configuration with two anchoring teeth and the rear region of the blade root as seen in the direction of rotation has a dovetail configuration with one anchoring tooth.
According to an advantageous second alternative embodiment of the invention, the front region of the blade root as seen in the direction of rotation has a fir tree configuration with a number of N anchoring teeth and the rear region of the blade root as seen in the direction of rotation has a fir tree configuration with a number of n anchoring teeth, such that the number N is greater than the number n.